1. Field of the Invention
The present invention relates to a method of crystal analysis and an apparatus for crystal analysis capable of analyzing crystalline states such as the crystallographic orientations of individual crystal grains on the surface of a specimen.
2. Description of the Related Arts
The recent development of micromachining technologies has come to require the technologies for analyzing crystal system and crystallographic orientations of crystal grains on a solid surface or the like. For example, a fine copper (Cu) wiring formed by a plating process has been employed for a coil wiring of a write element for a magnetic head employed in a hard-disk drive. In this copper wiring, the orientations of microcrystals and the structures of crystal-grain boundaries make a difference in a resistance value of the wire, causing variations in the characteristics of the magnetic head. For this reason, control of crystal growth has become one of the requirements for fabricating a magnetic head of high reliability and thus grasping of diameters of microcrystal grains, states of grain boundaries and crystallographic orientations has become of great interest.
Concerning the diameters of crystal grains and states of grain boundaries, it is easy to obtain knowledge through observations by an electron microscope and observations by a scanning ion microscope (SIM). As a practical method available for obtaining the knowledge specifically on the crystallographic orientations of the copper crystal grains that make up the copper wiring described above, however, there has been known only the EBSP (Electron BackScattering Pattern method or the Electron BackScattering diffraction Pattern) method. In the EBSP method, an electron beam impinges on a specimen at a large incidence angle in a scanning electron microscope (SEM); the electron beam experiences reflections and diffraction in the specimen; and is scattered backwards to form a diffraction image. This diffraction image (i.e., diffraction pattern) varies in its bandwidth and intensity depending on the crystalline structure at the incident position of the electron beam. Accordingly, the crystal system and the crystallographic orientation can be determined by analyzing the obtained diffraction pattern. Performing the analysis of the pattern while scanning a specimen surface with the electron beam enables obtaining the knowledge on the two-dimensional distribution of the crystallographic orientations on the specimen surface.
However, a problem has been that, because, in the EBSP method, the electron beam impinges on a specimen surface at a large angle of incidence, minute unevennesses of the surface affect on the result of the analysis and the correspondence between the distribution of the crystallographic orientations observed through the EBSP method and the microscopic image observed through the ordinary scanning microscopic photographs cannot easily be identified. Furthermore, because the diffraction pattern is caused by the Bragg reflection from crystal grains, it is basically difficult to have the resolution (ie., spatial resolving power) raised higher than the existing value, practically the resolution being of the order of several tens of nanometers.
An incidence angle described herein stands for the angle measured from the direction of the normal of the plane of incidence.
While a crystal system and a crystallographic orientation can be decided by the X-ray diffraction method as well, it is difficult in the case of the X-ray to narrow the beam and consequently the resolution is of the order of ten micrometers. Furthermore, the penetration depth of the X-ray is so deep that it is difficult to decide the crystallographic orientation in the outermost surface of a specimen. Japanese Patent Laid-open Publication No. H05-264477 (JP, 5-264477A) discloses a method of analyzing crystallographic orientations of the crystal grains in the surface layer of a specimen through the use of a X-ray, in which a collimated X-ray is applied to a specimen at a large angle of incidence, i.e., at a grazing angle along the specimen surface and, based on the obtained diffraction circles, the crystallographic orientations of the microcrystals in the surface layer are measured.
Japanese Patent Laid-open Publication No. 2003-21609 (JP, P2003-21609A) discloses a method of detecting a crystal axis of a specimen using the Rutherford backscattering analyzer of the parallel magnetic field type that has performance of converging the ions back-scattered from the specimen, the surface of which is irradiated with an ion beam, on the beam axis through the use of the magnetic field parallel to the incident ion beam. In this method, the distribution of detected quantity of the scattered ions is obtained making use of the two-dimensional ion detector and the detection of the crystal axis of the specimen is performed on the basis of the obtained distribution. This method, however, is problematic in that the measuring devices to be employed tend to be complicated, such as a two-dimensional ion detector, a parallel magnetic field generator and the like and in addition, a long measurement time tends to be required for measuring the two-dimensional distribution of the scattered ions.
As described above, the EBSP method is widely employed at present as a method of analyzing and identifying the crystal systems and crystallographic orientations of the crystal grains on a specimen surface made up of fine crystal grains. The EBSP method, however, is problematic in that because the electron beam impinges on a specimen surface at a large angle of incidence, minute unevennesses of the surface affect on the result of the analysis, and that the resolution is of the order of tens of nanometers. While alternatively to the EBSP method, there exist methods of analyzing and identifying the crystal systems and crystallographic orientations of fine crystal grains on a specimen surface, such methods are not necessarily practical as compared to the EBSP method.